Battery charger

ABSTRACT

A battery charger with charging parameter values derived from communication with a battery pack to be charged. Communication is over a one-wire bus with battery pack transmissions in response to charger inquiries. The battery charger may be in the form an integrated circuit driving a power transistor or other controllable DC supply. A battery pack may contain a program with multiple charging currents and charging interval termination methods such as time, temperature rise, and incremental voltage polarity. A lack of communication may be invoke a default charging program or denial of access to the charger. The charger also communicates over a high-speed three-wire bus with an external computer for analysis of identification information acquired from the battery and for control of the charger.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 08/764,285,filed on Dec. 12, 1996, now U.S. Pat. No. 5,694,024 issued on Dec.2,1997 which is a continuation of application Ser. No. 07/957,571, filedon Oct. 7, 1992, now U.S. Pat. No. 5,592,069.

United States patent application Ser. No. 953,906, filed Sep. 30, 1992,discloses related subject matter and is hereby incorporated byreference. This cross-referenced application is assigned to the assigneeof the present application.

PARTIAL WAIVER OF COPYRIGHT PURSUANT TO 1077 O.G. 22 (Mar. 20, 1987)

All of the material in this patent application is subject to copyrightprotection under the copyright laws of the United States and of othercountries. As of the first effective filing date of the presentapplication, this material is protected as unpublished material.

Portions of the material in the specification and drawings of thispatent application are also subject to protection under the maskworkregistration laws of the United States and of other countries.

However, permission to copy this material is hereby granted to theextent that the owner of the copyright and maskwork rights has noobjection to the facsimile reproduction by anyone of the patent documentor patent disclosure, as it appears in the United States Patent andTrademark Office patent file or records, but otherwise reserves allcopyright and maskwork rights whatsoever.

BACKGROUND AND SUMMARY OF THE INVENTIONS

The present invention relates to electronic devices, and, moreparticularly, to devices useful for battery charging.

Battery Chargers

The widespread use of battery-powered portable computers (e.g.,notebooks, laptops and palmtops) with high performance relies onefficient battery utilization. In particular, portable computerstypically use rechargeable batteries (e.g., lithium, nickel-cadmium, ornickel metal hydride) which weight just a few pounds and deliver 4 to 12volts. Such batteries provide roughly three hours of computing time, butrequire about three times as long to be recharged. Such slow rechargingis a problem and typically demands that users have several batterieswith some recharging while others are being used.

Known battery chargers apply a constant voltage across a dischargedbattery with the applied voltage determined by the maximum voltageacceptable by the battery. FIG. 1a heuristically illustrates such abattery charger with V_(MAX) the maximum voltage acceptable by thebattery and I_(MAX) the maximum current; the resistor R and V_(MAX) arethe adjustable values. FIG. 1b is the load line for the battery chargerof FIG. 1a and shows the charging current I as a function of the batteryvoltage V. As the load line shows, the charging current begins atI_(MAX) with a totally discharged battery as indicated by point A. Thebattery rapidly charges and its voltage increases and the chargingcurrent decreases with the operating point moving down the load line asshown by arrow B. Then as the battery voltage rises to near V_(MAX), thecharging current falls to zero as indicated by point C. And the smallcharging current implies a large charging time. Indeed, most of thecharging time will be during operation approaching point C.

Furthermore, the different chemistries of various battery typespreferably use differing recharging voltages, and varying batterycapacities (sizes) demand differing charging currents. However, knownbattery chargers cannot automatically adapt to such a variety chargingconditions and remain simple to use.

Features

The present invention provides battery charging with charging parametervalues selected by communication with imbedded information in a batterypack and then adjusted during charging. This permits adaptation tovarious battery chemistries and capacities, and, in particular, allowsfor approximately constant current charging at various current levelsand for trickle charging.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with reference to theaccompanying drawings, which are schematic for clarity.

FIGS. 1a-b illustrate known battery chargers and their load lines;

FIG. 2 is schematic functional block diagram of a first preferredembodiment battery charger;

FIG. 3 is a state diagram for the first preferred embodiment;

FIG. 4 is a flow chart for communication by the first preferredembodiment;

FIGS. 5-7 show communication waveforms; and

FIG. 8 illustrates identification memory organization.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Functional Overview

FIG. 2 is a schematic functional block diagram of a first preferredembodiment battery charger, denoted generally by reference numeral 200,connected to charge battery pack 250 with imbedded one-wirecommunication module 252. Battery charger 200 includes power transistor202, current sense resistor 204, voltage sense node 205, temperaturesensor 206 affixed to battery pack 250, ambient temperature sensor 207,controller 210, operational amplifier 214, power transistor driver 218,one-wire bus 220, and three-wire bus 223. Portion 270 of battery charger200 may be formed as a single integrated circuit and provide low costand ruggedness.

Battery charger 200 can provide battery charging up to about 20 voltswith 2.5 amp currents; this demands a separate power transistor 202 forcooling. (More generally, power transistor 202 could be replaced by aDC-to-DC converter.) Battery pack 250 may have various numbers of cellsand cells of various chemistries which require various chargingprograms. Controller 210 acquires information about battery pack 250through inquiry over the one-wire communication bus 220. In particular,module 252 within battery pack 250 contains identification plus chargingparameter values, such as maximum voltage V_(MAX) and maximum currentI_(MAX) along with charge time and endpoint detection method. Controller210 reads the identification and charging parameter values andconfigures itself accordingly. Note that the identification can be usedfor access control: charger 200 can refuse to charge a battery pack withan invalid identification. Controller 210 also has stored (innonvolatile ROM) default charging parameter values. Thus when controller210 is unable to read charging parameter values from battery pack 250,it may read from its own ROM for default parameter values. Afteracquisition of parameter values, charger 200 begins charging batterypack 250. Charger 200 may also communicate at high speed over itsthree-wire bus 223 with a computer or other controller; this permitsexternal analysis of the identification and charging parameter valuesread from module 252 plus external control of access and the chargingparameter values.

Operation

FIG. 3 is a state diagram for charger 200 which describes its operationand the charging parameters used. Charger 200 begins in the upperrighthand circle of FIG. 3 which represents the state of no power supply(PF=1). No power implies no charging current (I=0) because powertransistor 202 cannot be turned on. Also, the charging timer withincontroller 210 will not be running (TMRRST=1). Controller 210 has aninternal voltage regulator, so a 25 volt power supply may be used asillustrated to provide charging of multicell battery packs.

When power is supplied to charger 200 (PF=0), it first checks the inputsof temperature sensors 206 and 207; and if the battery temperature (TB)is less than the upper temperature limit for trickle charge (T5) and ifthe ambient temperature (TA) is greater than the lower temperature fortrickle charge (T0), charger 200 moves to an initial trickle chargestate of applying a trickle charge current (I3). The circle in thecenter of FIG. 3 represents this initial trickle charge state (I=I3).The trickle charge current level is maintained by feedback fromamplifier 214 measuring the charging current and then driving powertransistor 202. This initial trickle charge state does not have thecharging timer running (TMRRST=1) but does immediately detect thepresence or absence of a battery pack 250 by detecting a positive orzero voltage at the voltage sense node 205. If no battery pack 250 isconnected (BDET=0) or if a power failure occurs (PF=1), then charger 200reverts back to the no power state. Contrarily, if charger 200 detectsthe presence of a connected battery pack, then charger 200 moves to theone-wire communication state represented by the circle in the upperlefthand corner of FIG. 3. That is, the initial trickle charge state isjust a transient state.

In the one-wire communication state charger 200 maintains the tricklecharge current to the connected battery pack 250 (I=I3) and the chargingtimer remains off (TMRRST=1). Further, charger 200 sends a reset signalover the one-wire communication bus 220 to initiate a read (1 WIRE RD)of the identification and charging parameter values in module 252 ofbattery pack 250. Charger 200 either reads a recognizable identificationto permit charging or not. When an acceptable identification is read butno charging parameter values, module 252 reads from its ROM defaultcharging parameter values. Controller 210 loads the charging parametervalues into registers to configure its various subcircuits forcomparisons of measured charging parameters with the loaded values. Ifat any time during this one-wire communication power fails or batterypack 250 is disconnected or the ambient temperature falls below thetrickle charge minimum or the battery temperature rises above thetrickle charge maximum, charger 200 reverts to the no power state.Otherwise, after completing the one-wire communication (OWRCMPLT=1),charger 200 again checks the ambient and battery temperatures fromsensors 206 and 207 and if the battery temperature is less than theupper temperature for rapid charge (T3) and if the ambient temperatureis greater than the lower temperature for rapid charge (T2), thencharger 200 switches to a state of rapid charge represented by thecircle in the lefthand center of FIG. 3. However, if the temperatures donot satisfy the inequalities, charger 200 stays in the one-wirecommunication state and provides a trickle charge I3 to battery pack 250until either a temperature changes, battery pack 250 is disconnected, orpower failure occurs. Note that the rapid charge current level andtemperature limits may be parameter values read from module 252.

In the rapid charge state controller 210 drives the charging current upto I1 and starts the charging timer (I=I1 and TMRRST=0). If there is apower failure or battery pack 250 is disconnected, then charger 200again reverts to the no power state; otherwise, the rapid charge statepersists and charger 200 supplies a charging current I1 to battery pack250 until one of the following occurs: (1) the battery voltage parameter(VBAT) measured at node 205 exceeds the parameter value (VBATLIM) readfrom module 252, (2) the parameter battery voltage delta (peak batteryvoltage sensed at node 205 so far during the charging minus the batteryvoltage now sensed)(DELV) exceeds the parameter value (DELVLIM) readfrom module 252 and the charging timer has been running for more than 5minutes, (3) the charging timer has been running longer than the timefor rapid charge parameter value (t0LIM) read from module 252, (4) theambient temperature is below parameter value T2, (5) the batterytemperature is above parameter value T3, or (6) the battery temperaturedelta (equal to TB-TA)(DELT) exceeds the parameter value (DELTLIM) readfrom module 252. When one of these six events occurs, charger 200 movesto the standard charge state represented by the circle in the lowerlefthand portion of FIG. 3. Note that the rapid charge terminationevents of significance depend upon battery cell chemistry; for example,nickel-cadmium cells have a voltage drop near maximum charge. This makesa positive battery voltage delta DELV a good indicator of full charge,with the size of a significant DELV varying with the number of cells inseries in battery pack 250. Similarly, nickel-cadmium cells charge by anendothermic reaction and thus the battery temperature will not riseuntil full charge; this makes the battery temperature delta DELT anothergood indicator of full charge. Again, these parameters values such asDELTLIM, t0LIMIT, T2 may have been read from module 252 or could havebeen acquired over three-wire communication in the case of no module252.

In the standard charge state controller 210 drives the charging currentto I2 and restarts the charging timer (I=I2 and TMRRST=0). If there is apower failure or battery pack 250 is disconnected, then charger 200again reverts to the no power state; otherwise, the standard chargestate persists and charger 200 supplies a charging current I2 to batterypack 250 until one of the following events occurs: (1) the batteryvoltage (VBAT) sensed node 205 exceeds the maximum battery voltageduring charge (VBATLIM), (2) the charging timer has been running longerthan the maximum time for standard charge (t1LIM), (3) the ambienttemperature is below the lower temperature limit for standard charge(T1), or (4) the battery temperature is above the upper temperaturelimit for standard charge (T4). When one of these four events occurs,charger 200 moves to the trickle charge state represented by the circlein the lower center of FIG. 3.

In the trickle charge state controller 210 drives the charging currentback to I3 to stops the charging timer (I=I3 and TMRRST=1). If there isa power failure or battery pack 250 is disconnected or the batteryvoltage VBAT exceeds the maximum VBATLIM then charger 200 once againreverts to the no power state; otherwise, the trickle charge statepersists and charger 200 supplies a charging current I3 to battery pack250 until either (1) the ambient temperature is below T0 or (2) thebattery temperature is above T5. When one of these two events occurs,charger 200 moves to the standby state represented by the circle in thelower righthand portion of FIG. 3.

In the standby state controller 210 turns off power transistor 202 andstops the charging timer (I=I3 and TMRRST=1). If there is a powerfailure or battery pack 250 is disconnected, then charger 200 once againreverts to the no power state; otherwise, the standby state persistswith charger 200 not supply any charging current I3 to battery pack 250until either (1) the ambient temperature is rises above T0 or (2) thebattery temperature falls below T5. When one of these two events occurs,charger 200 returns to the trickle charge state from whence it came andrepeats itself.

One-Wire communication

FIG. 4 is a flow chart of the communication by charger 200 with batterypack module 252, and FIGS. 5-7 illustrate signalling waveforms duringone-wire communication. Controller 210 pulls the data line ofcommunication bus 220 high (+5 volts) and this supplies the power tomodule 252 which includes an energy storage capacitor. The transientinitial trickle charge state of charger 200 provides time for module 252to store sufficient energy in its storage capacitor to power up itscircuitry. Module 252 only responds to signals from controller 210, andthus only requires power when communicating. Thus module 252 cancommunicate with controller 210 even when battery pack 250 is fullydischarged.

The flow shown of FIG. 4 begins with Battery Detect=1 which is thedetection of battery pack 250 connected to node 205; this corresponds tothe movement from the initial trickle charge state to the communicationstate in FIG. 3. Controller 210 detects battery pack 250 by noting apositive voltage at node 205 which derives from residual charge ofbattery pack 250 and initial charging by trickle charge being applied inthe initial trickle charge state.

Once battery pack 250 has been detected, controller 210 applies a resetsignal on the data line of one-wire bus 220 by driving the data line low(ground) for about 480 microseconds (μs) and then pulling the data linehigh (+5 volts) for about 480 μs. In response to the 480 μs low resetsignal, module 252 signals its presence with a presence detect signal bypulling the data line low during the 480 μs high. The pulldown in module252 overpowers the pullup of controller 210, so the data line goes lowand controller 210 senses the low. Module 252 generates a nominal 120 μstime period for the pulldown presence detect pulse and applies thispulldown beginning a nominal 30 μs after controller 210 has returned thedata line high. However, this time period may vary by a factor of 2amongst modules, so controller 210 samples the data line at 65-70 μsafter it has returned the data line high. See FIG. 5 which shows thewaveforms on the data line. Controller 210 may repeatedly apply resetsignals on the data line in order to account for the delay in theconnection of one-wire bus 220 to battery pack 250 after the connectionto node 205.

If the sampling of the data line by controller 210 does not reveal apresence detect signal (Reconfigurable=1 not true in FIG. 4), thencontroller 210 will use its default charging parameter values by readingthem from its memory (Default Parameters Available and Load Configur RAMFrom EEPROM in FIG. 4). Conversely, if controller 210 senses the dataline low (Reconfigurable=1), then it continues with one-wirecommunication and drives the data line low for 1+μs and then pulls thedata line high again to allow the response of module 252 to control thedata line. Module 252 responds to the high-to-low transition by readingthe first bit in its memory onto the data line: when the first bit is a0, then module 252 pulls down the data line for a nominal 30 μs so ineffect the data line remains low and controller 210 detects this bysampling after 15 μs. FIG. 6 shows the read 0 waveforms on the dataline. Contrarily, when the first bit is a 1, then module 252 letscontroller 210 pull up the data line; see FIG. 7. This process of ahigh-to-low by controller 210 followed by a pulldown or no pulldownresponse of module 252 proceeds through the memory of module 252 untilall 320 bits (64 identification bits plus 256 charging parameter valuebits) have been read. The total read time thus may be less than 50milliseconds.

Module 252 has two memories: a 64-bit ROM for identification and a256-bit EEPROM for charging parameter values. FIG. 8 illustrates thecontent of the 64 bits of ROM. In particular, the first eight bitsindicate the family of modules to which module 252 belongs (FamilyCode=Charger in FIG. 4). If this family is for a battery pack with amanufacturer's identification (Use Manufacturer ID in FIG. 4), then thenext sixteen bits read (B8-B23= Manufacturer ID) may be decoded to checkidentification of the manufacturer of battery pack 252 and perhapsprevent charging by charger 200. Lastly, after 64 bits have been readfrom the ROM, controller 210 applies a Cyclic Redundancy Check (CRC)algorithm to the first 56 bits to compare to the last eight bits toverify that the communication was error free (Verify ROM CRC).

After reading the ROM of module 252, controller 210 then reads the 256bits of EEPROM to get charging parameter values for operation (ReadConfig Data Into Charger Config RAM). The reading of the parametervalues is also checked by a CRC byte (Verify RAM CRC). Once the EEPROMhas been read, the one-wire communication is complete (One Wire ReadComplete in FIG. 4 and OWRDMPLT=1 in FIG. 3). Charger 200 then switchesinto the rapid charge state using the charging parameter values readfrom module 252.

U.S. Pat. No. 5,045,675 contains a discussion of one-wire communicationand serial memory reading and is hereby incorporated by reference.

Further Modifications and Variations

The preferred embodiments may be modified in many ways while retainingone of more of the features of a battery charger with charging parametervalues selected by communication with a battery pack to be charged andusing multiple constant charging currents with multiple endpointdeterminants. For example, the memory in the battery pack could be allROM or all EEPROM, or EPROM, a mixture of two memory types; thecommunication could be over full duplex or other than one-wire, and thememory may have its own power supply to be operative with a dischargedbattery pack; sensors for endpoint determinants other than temperatureincrement and voltage increment may be used; the power transistor couldbe a switching AC-DC converter or a switching DC-DC converter; thecontroller may have nonvolatile memory or just registers for holdingcharging parameter values; and so forth.

What is claimed is:
 1. A battery pack comprising:a memory; at least onerechargeable cell; and a communication terminal coupled to saidmemory,wherein said memory contains information with respect to at leastone charging parameter of said battery pack and wherein said informationis supplied to said communication terminal and wherein saidcommunication terminal is capable to be connected to a battery chargingdevice and wherein a plurality of data bits is transmittable to saidbattery charging device through said communication terminal.
 2. Abattery pack as in claim 1, wherein said memory contains at least onebit as to the condition of said battery pack.
 3. A battery pack as inclaim 2, wherein said at least one bit indicates that a differentcharging voltage should be supplied to said battery pack by a chargingdevice.
 4. A battery pack as in claim 2, wherein said at least one bitindicates that no charging energy should be supplied to said batterypack by a charging device.
 5. A battery pack comprising:at least onerechargeable battery cell; a memory containing information related tothe charging of said battery pack; at least one sensor selected from thegroup of temperature sensors, voltage sensors, current sensors orpressure sensors; means to store an output from said at least one sensorin said memory; and a communication terminal coupled to said memorywherein there is the capability of transmitting a plurality of data bitsof information from said memory to an external system through saidcommunication terminal.
 6. A battery pack comprising:at least onerechargeable cell; a memory containing digital information about saidbattery pack; and a communication terminal coupled to said memory whichis capable of connecting said battery pack to a charger such that aplurality of data bits are capable of being transmitted which arerepresentative of at least some of said digital information from saidmemory to a charger, such that the charger would be capable to select adifferent phase of a given charging procedure in response to informationtransmitted from said battery pack over said communication link.
 7. Abattery pack as in claim 6, wherein the information that is capable ofbeing transmitted is at least a bit indicative of a voltage level to besupplied by a charger.
 8. A battery pack as in claim 6, wherein theinformation that is capable of being transmitted returned in response toan inquiry made by a charger.
 9. A battery pack as in claim 6, whereinsaid memory contains at least one bit indicative of a detected failureof said battery pack.
 10. A battery pack comprising:at least onerechargeable cell; a memory; and a communication terminal capable ofcoupling said memory to a charging device,wherein said memory containsat least one parameter associated with said battery pack and whereinsaid at least one parameter is selected from the group of a chargingvoltage to be supplied to said battery pack, a charging current to besupplied to said battery pack, a not-exceed-temperature limit forcharging of said battery pack, an identification number of said batterypack, and a counter for the number of charge cycles of said batterypack, the manufacturer of said battery pack or a combination thereof;and wherein said communication terminal is capable of transmitting aplurality of data bits indicative of at least one of said parameters.11. A battery pack comprising:a memory; at least one rechargeable cell;a communication terminal coupled to said memory wherein said terminalprovides a link capable of transmitting information stored in saidmemory of said battery pack to a charging device; andwherein said memorycontains information with respect to at least one charging parameter ofsaid battery pack and wherein a plurality of data bits indicative ofsaid information is supplied to said communication terminal fortransmission to the charging device.
 12. A battery pack as in claim 11,further comprising:at least one sensor selected from the group of atemperature, voltage and current; and means to store an output from saidat least one sensor in said memory.
 13. A battery pack as in claim 12,wherein said memory contains at least one bit as to a condition of saidbattery pack.
 14. A battery pack as in claim 13, wherein said at leastone bit indicates that a different charging voltage should be suppliedto said battery pack by a charger.
 15. A battery pack comprising:atleast one rechargeable cell; a memory containing digital informationabout said battery pack; a communication terminal coupled to said memoryand providing the capability of transmitting a plurality of data bitsindicative of at least some information from said memory to a hostsystem, such that the host system is capable of selecting a differentphase of a charging procedure of said battery pack in response toinformation transmitted from said battery pack through saidcommunication terminal.
 16. A battery pack as in claim 15, whereincommunicated information from said battery pack is at least a bitindicative of a voltage level to be supplied by a charger.
 17. A batterypack as in claim 15, wherein communicated information from said batterypack is returned in response to an inquiry made by the charger.
 18. Abattery pack comprising:a memory containing profile informationconcerning said battery pack; at least one rechargeable cell; and anelectronic communication terminal coupled to said memory and configuredso as to be capable of transmitting a plurality of bits of informationstored in said memory to a charging device,wherein said profileinformation is information with respect to a characteristic of saidbattery pack and wherein said information is supplied to said electroniccommunication terminal and wherein said electronic communicationterminal provides a link to transmit a plurality of data bitsrepresentative of at least part of said profile information.
 19. Abattery pack comprising:a means to couple said battery pack to a pieceof associated equipment; a rechargeable battery cell, a memory capableof storing cell manufacture data; a communication terminal coupled tosaid memory, wherein said communications terminal is configured so as tobe capable of transmitting a plurality of data bits indicative of saidcell manufacture data to a charger.
 20. A battery pack comprising:amemory containing profile data concerning said battery pack; at leastone rechargeable cell; a communication terminal configured so as to becapable of transmitting information stored in said memory of saidbattery pack to a charging device; andwherein said communicationterminal is configured so as to be capable of transferring informationfrom said stored profile data which comprises at least one chargingparameter of said battery pack.